"Bullet hole — a small stone from the universe went through our solar array," he posted to his Twitter account. "Glad it missed the hull."

'Glad', indeed.

If that tiny piece of whatever-it-was had slammed into Earth's atmosphere, it would have simply burned up (and given someone a nice, if brief, light show if it happened on the night side of the planet). However, the random objects flying around up there (man-made or otherwise) have the potential to do damage to anything we have have in orbit. Any kind of space junk that's been left behind by rocket launches over the years is probably traveling at around 10 km/s, or 36,000 km/h. Meteoroids can be going faster, though, as the typical speeds used to model meteor and asteroid collisions are between 11-17 km/s (39,600-61,200 km/h).

Something small enough to create that little 'bullet hole' wouldn't have been able to get through the layers of the station's hull, though, since it's specifically built to withstand impacts from these 'micrometeoroids' or small pieces of space junk. However, there are much bigger objects flying around, both in orbit and through our local space, and they aren't always big enough to be able to detect them.

The ISS astronauts were very lucky that it wasn't the size of a baseball or a basketball.

(Photos courtesy: Commander Hadfield/NASA)

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